1. Field of the Invention
The present invention relates generally to voltage references. In particular, the present invention relates to low temperature coefficient low power programmable complementary metal oxide semiconductor (CMOS) voltage references with simple and efficient architecture.
2. Description of the Related Art
Historically, the design of voltage references entailed the use of circuits containing hundreds of transistors. Due to this, the complexity and costs involved in designing such voltage references can be significantly high. Bandgap voltage reference circuits are most commonly used in CMOS mixed signal circuits to provide for a stable voltage reference. A standard bandgap reference such as, for example, LM330 3-Terminal Positive Regulator from National Semiconductor Corporation, has a variation of approximately 0.2% in output voltage over a temperature range from room temperature to 80.degree. C. Moreover, as voltage references, erasable programmable read-only memories (EPROMs) are designed to support leakage on the order of 1 volt over a ten (10) year lifetime.
However, the bandgap circuit has a number of shortcomings. Some of these shortcomings include large dc power consumption, the need for parasitic, and usually unsupported, pnp or npn transistors, and the need to match the base emitter voltage (V.sub.BE) for these parasitic devices. Additionally, several design iterations are often necessary to get the bandgap circuit to operate due to lack of good models for the second order effects upon which the bandgap performance is based. Moreover, the stability of the bandgap references over time has been a reliability issue for some CMOS products, for example, in telecommunications devices.